Micro-electronic components, i.e., integrated circuits, are presently used as component parts in a wide variety of electronic devices, for example, calculators, watches, organizers, cordless telephones, radios and tape recorders. The portability of such devices has created the need for miniature power cells which must produce increased energy per unit volume and superior discharge characteristics over conventional batteries. This need has lead to the development of relatively small, thin batteries which are constructed with an alkali metal anode, a non-aqueous electrolyte and cathodes which are constructed of non-stoichiometric compounds. Lithium is an especially suitable material for construction of the anode due to its relatively low molecular weight and high electrode negativity. Such small, thin solid state batteries can be made with a high energy density, a long shelf life, and are able to operate efficiently over a wide temperature range.
These thin, batteries are conventionally constructed in the form of a container referred to as a coin cell. The container includes a cylindrical housing (or can) and a lid (or anode cap) which are typically formed of nickel clad stainless steel. Typically such a battery is assembled by assembling the anode, separator, electrolyte and cathode components of the battery with the lid and then crimping the lid and housing together with a gasket therebetween. As thus assembled, the housing is in electrical contact with the cathode of the battery and the lid with the anode.
In the past these coin cell batteries were typically manufactured such that the lid provided the negative contact surface, while the housing on the opposite side of the battery provided the positive contact surface. By separating the positive and the negative contact surfaces of the coin cell battery, the likelihood of shorting the battery was thought to be minimized.
Because the battery contact surfaces were on opposite sides of the battery, the contacts of the device into which the battery was installed needed to contact the appropriate contact surfaces of the battery. Because each of the device contacts needed to physically contact an opposite side of the battery, the device contacts have also been used to assist in preventing movement of the battery with respect to the device.
The necessity of a device contact on each side of the battery required a physical structure on both sides of the battery when installed. Normally a deformable contact was provided on either side of the battery. The battery was then inserted between the device contacts and the pressure and the friction exerted by the device contacts retained the battery in place. Another method of retaining the battery within the device was to provide a recess in the device with a contact surface at the bottom of the recess. The battery was then installed into the recess. The second contact surface was provided on a device cover mating with the recess. Once the device cover was installed, it was in electrical contact with the remainder of the device and could act to transfer the current.
One of the problems associated with structures like those described above, which were designed to receive a battery having its contact surfaces on either end, is that the minimum thickness necessary to receive the battery was the sum of the battery thickness and the two contact assemblies at either end. As is apparent this does not provide a compact assembly.
There is, then, a need in the art for a battery and a battery contact assembly that minimizes the thickness required to receive the battery and which minimizes the complexity and time required for assembly. Accordingly, it is an object of the present invention to provide a battery and a battery contact assembly that are inexpensive and easy to manufacture, yet offering a high degree of reliability to minimize the possibility of electrical shorting across the terminals of the battery. It is another object of the invention to provide a battery having the contact surfaces of both terminals arranged to be substantially co-planar. It is yet another object of the invention to provide a support substrate for a battery having the contact surfaces of both terminals insulated from one another but contained in substantially a single plane. It is a still further object of the invention to provide a battery contact assembly wherein an electrically conducting adhesive is used to adhere the battery to a substrate and to establish an electrical connection to contacts on the substrate.
Other objects, advantages and capabilities of the present invention will become more apparent as the description proceeds.